This disclosure relates to the oversteer control of a motor vehicle, and, more particularly, to the simultaneous use of vehicle state sensors to control motor vehicle oversteer through active and passive steering mechanisms.
Motor vehicle handling instabilities are generally a function of the yaw behavior of the motor vehicle and the motor vehicle speed. The yaw behavior is caused by the lateral movement of the motor vehicle and is most often the result of a combination of operator input and road surface conditions. Such lateral movement may occur in response to the oversteering of the motor vehicle. Oversteering, which generally results in the motor vehicle articulating a turn that is too tight, may provide less than optimal handling of the motor vehicle, especially when maneuvering the motor vehicle through rapid or sharp corners.
Various arrangements for compensating for the oversteering of motor vehicles have typically been attained by relating the yaw behavior of the motor vehicle to the braking function. One particular arrangement involves the comparison of a vehicle yaw angular velocity required value and an actual vehicle yaw angular velocity of the motor vehicle. In such an arrangement, the vehicle yaw angular velocity required value is formed from measured quantities such as motor vehicle speed and steering wheel angle. The actual vehicle yaw angular velocity is measured using a gyroscope or other device. The difference between the yaw angular velocity required value and the yaw angular velocity actual value is calculated and is used to represent a detected handling situation or yaw behavior of the motor vehicle. A critical detected handling situation is deduced when the yaw angular velocity actual value deviates from the yaw angular velocity required value. This detected deviation is then used to minimize the motor vehicle yaw by the independent braking or acceleration of the individual wheels of the motor vehicle.
Other arrangements for compensating for vehicle yaw moments utilize the suspension aspects of the motor vehicle. In such arrangements, yaw moment sensors apply varying distributions of loading to the lateral wheels of the motor vehicle to induce xe2x80x9cdriftxe2x80x9d or movement of either the front or rear end of the motor vehicle to correspond with a line of travel of the motor vehicle. In order to effectuate such applications, the motor vehicle typically includes devices for detecting and quantifying the cornering and acceleration of the motor vehicle. Devices for applying the varying distributions of loading to the lateral wheels are communicably linked to the cornering and acceleration devices and produce yaw moments in the direction of an oversteering condition. By inducing yaw moments in the direction of an oversteering condition, unwanted drift of the motor vehicle can be alleviated.
A system and a method for compensating for the oversteer of a motor vehicle is described herein. The system includes a controller in operable communication with a steering system of the motor vehicle. The controller may be configured to receive input signals from at least one sensor and may also be configured to process the input signals to produce an output signal that is capable of being received by the steering system of the motor vehicle. The input signals may include a steering pinion gear angle signal, a vehicle velocity signal, and a yaw rate signal. The output signal may be received by a motor that is configured to provide power assist to the steering system in an effort to maintain the stability of the motor vehicle during an oversteer condition. The stability of the motor vehicle is typically maintained through control of the steering system, which may or may not be autonomous. Furthermore, the stability of the motor vehicle may be maintained by the manipulation of at least one steerable wheel of the motor vehicle.
The method for compensating for the oversteer of the motor vehicle includes receiving signals into the controller, producing at least one transmittable output signal to the steering system of the motor vehicle, and articulating at least one steerable wheel in response to the output signal. Receiving the signals into the controller typically may include receiving signals corresponding to a yaw angular velocity actual value and a required yaw angular velocity value. Receiving the required yaw angular velocity value signal may include receiving a steering pinion gear angle signal, receiving a motor vehicle velocity signal, and mathematically combining the two signals. The output signal may then be produced by determining the difference between the required yaw angular velocity and the yaw angular actual value signal with respect to time. The articulating of the steerable wheel is typically effectuated through a mechanical manipulation of either the electric power steering system or the steerable wheels.